The netmsg.tar.Z file is a compressed tar file of the netmsgserver sources
for Mach 2.5 as of April 1992. They should be un-tarred into a clean
source directory and will be arranged into 4 subdirectories.

The Makefiles in those directories include the file Make.inc which
in turn includes Makefile-common. These are files that define commonally
used make definitions and rules  In our source tree Makefile-common
lives in /afs/cs/mach/src, Make.inc lives in /afs/cs/mach/src/usr/misc/.mach
and the netmsgserver sources live in /afs/cs/mach/src/usr/misc/.mach/etc/
netmsgserver. Depending on where you put the Make.inc and Makefile-common 
files, you will need to change the pathnames in the include statements.